1. Field of the Invention
The present invention relates to a method for standby control in a mobile telecommunication network, more particularly to a method for standby control in a base station and mobile unit in a mobile telecommunication network and to a mobile unit using the same.
Control information transmitted between a base station and a mobile unit is sent via a specially provided common radio control channel or is sent via an individual radio speech channel assigned to each mobile unit. The present invention relates to the former radio control channel.
There are various types of information which are sent over the radio control channel, but the present invention is concerned in particular with the broadcast information sent from the base station side to the mobile units in a standby state.
2. Description of the Related Art
In a mobile telecommunication network, a base station covers a certain service zone using a carrier (electric wave) having a frequency assigned to that base station. A mobile unit moving in the zone communicates with another party through the base station.
The base station broadcasts information to all the mobile units in the standby state in its zone. The mobile units execute certain control processes based on the received broadcast information to engage in calls.
The broadcast information is sent from the base station periodically via the previously mentioned common radio control channel.
The portions of the broadcast information particularly relevant to the present invention are the "standby enabling condition" and the "standby disabling condition". A typical "standby enabling condition" is the standby enabling level. When above that level, a mobile unit can start a call.
On the other hand, a typical "standby disabling condition" is the standby disabling level. If less than this level, the mobile unit cannot start a call. Further, the "standby disabling level" has another meaning. That is, it means the level at which a normal call quality can no longer be guaranteed when a mobile unit engaged in a call begins to leave a zone. In this case, "outside zone" is shown on the display of the mobile unit.
As explained above, a mobile unit is able to originate or receive a call when the level of reception is higher than a specific standby enabling level. On the other hand, it is inhibited from originating or receiving a call whenever the level is less than the specific standby disabling level.
Even if engaged in a call, the "outside zone" indication is given when the level falls below the standby disabling level.
The recent advances being made in mobile telecommunication networks have led to a tremendous rise in the number of users. Along with this, various modes of communication other than normal speech have been started.
The modes of communication differ depending on the differences in the types of the mobile units as well. Compared to communication using a car-mounted unit, communication using a handheld unit features much worse communication conditions, such as a far greater loss. Further, the modes of communication differ depending on whether the car-mounted unit or a car carrying a handheld unit is moving fast or slow. The following problem results from these differences in the modes of communication.
When setting a single standby enabling level so as to ensure the quality to be satisfied in normal speech as in the past, the "outside zone" display is given when the quality of communication for normal speech cannot be met. It therefore no longer becomes possible to make a call even when an emergency situation arises despite the urgent need to make the call. Considered from the opposite viewpoint, if a single standby enabling level is set considering only emergency situations, then while calls can be made in emergencies, the quality of communication would become extremely poor for a mobile unit at the fringes of a service area at the time of a normal calls.
Also, if a single standby enabling level is set to the quality to be satisfied in a normal speech call, when used for transferring data, where a higher quality is sought than normal speech calls, errors will be caused even in locations good enough for normal speech calls.
Considering this from the opposite viewpoint, if a single standby enabling level is set considering only data transfer, then there will be the trouble of a call not being possible due to the standby enabling level not being met despite a level of reception sufficient for speech calls from the standpoint of the mobile unit.
This means that in the case of an emergency such as a traffic accident, a mobile unit located at a position somewhat away from the zone would not be able to notify the authorities of the emergency. This means the failure of the basic function of a telecommunication network.